College of Science, University of Thi-Qar discussed a Ph.D. thesis on the behavior of quantum dots with double filtered optical feedthroughs by the postgraduate student, Mr. Alaa Saleh Mahdi.

The thesis reviewed a study of the complex kinematics of quantum dot semiconductor lasers (QDSL) under the influence of optical feedback (OFB), filtered feedback (FOF), double-filter optical feedback (DFOF) and analyzing it with the help of the MATLAB program.

The thesis highlighted that the QDSL system with OFB contains four differential equations that include the amplitude of the natural LASER field in the cavity, the probability of occupying the quantum dot (QD) LASER in the excited and ground states, and the number of carrier waves in the tank for each QD, which were proposed and then studied analytically.

The thesis concluded that the second FOF allows rich modulation of the laser frequency. Analysis of DFOF LASERs focuses on fundamental solutions, sometimes referred to as continuous wave (CW) or external filter modes (EFM), which result in a LASER output with constant amplitude and frequency according to numerical calculations.